The Single Ventricle HLHS – History Embryology Genetics Epidemiology

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The Single Ventricle HLHS – History Embryology Genetics Epidemiology

Raciatti, John, Host has reference to this Academic Journal, PHwiki organized this Journal The Single VentricleKarim Rafaat, M.D.The title “single ventricle” includes those lesions designated as bothHLHSHRHSHLHS is far more common, in addition to the strategy as long as palliation of both lesions similar, so I will not mention HRHSHLHS – HistoryFirst described in 1952 by Lev as the pathologic complex “hypoplasia of the aortic tract”, included cases of:hypoplasia of the aorta in addition to VSDhypoplasia of the aorta with aortic stenosis or atresia, with or without mitral stenosis or atresiaIn 1958, Noonan in addition to Nadas termed these lesions as “hypoplastic left heart syndrome”.

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EmbryologyThe embryologic cause is not fully understood.It probably results from a limitation of either LV inflow or outflow, such as the development of severe AS earlyDecreased antegrade flow through LVmost common cause is mitral atresiadecreased division of cardiac myocytes GeneticsFamilial inheritance:Autosomal recessive in addition to multifactorial inheritance have both been postulated.Sibling recurrence risk: 0.5%Sibling recurrence as long as all other cardiac mal as long as mations: 2.2%Definable genetic disorder (28%):Turner Syndrome Noonan SyndromeTrisomy 13, 18, 21, or other microdeletion syndromesEpidemiologyUni as long as mly lethal prior to 1980Each year, approximately 1000 infants with HLHS are born in the US.Prevalence: 1 per 6000-7000 live births.In pathologic series, it accounts as long as 1.4-3.8% of congenital heart disease.Third most common cause of critical CHD in the newborn. 23% of all neonatal mortality from CHDMale predominance: 57-70%.

AnatomyUnderdevelopment of the left side of the heart atresia of the aortic or mitral orifice hypoplasia of the ascending aorta.The left ventricle may be small in addition to nonfunctional or totally atretic Pulmonary venous return from LA to RA through a large PFO or ASDSystemic venous blood mixes with pulmonary venous blood in the RA in addition to RVRV ejects blood into a large MPASystemic circulation is supplied in parallel with pulmonary circulation through a PDAMultiple obstructions to systemic flowAortic valve atresiaArch hypoplasiaPlace systemic flow at risk

Blood flow to the coronary in addition to cerebral circulations is retrogradeUsually little or no flow through aortic valvePostnatal decline in PVR places systemic, in addition to especially the ductal dependant in addition to retrogradely supplied coronary in addition to cerebral vascular beds at risk as long as hypoperfusion secondary to pulmonary run-off PathophysiologyRelative Qp in addition to Qs determined via resistances of respective vascular bedsVentricle must supply both Qp in addition to QsSingle right ventricle has at least twice the volume load of an in series ventricleSignificantly volume overloadedThe aim of initial management is to optimize Qp in addition to Qs in a manner that provides adequate end organ oxygen delivery without overloading the single ventricleRemember my last lectureThis balancing act is only temporizing in addition to serves to allow pt to survive to definitive treatment

Treatment optionsSupportive careOnly option up to 25 years agoIs still main option of treatment in many countriesStaged reconstructionStage I Norwood ProcedureStage II Bi-directional Glenn or Hemi-FontanStage III Fontan ProcedureTransplantGoals of SurgeryUnobstructed systemic blood flowTo maximize oxygen delivery in addition to minimize ventricular hypertrophyLimited pulmonary blood flowTo minimize ventricular volume load in addition to the risk of pulmonary hypertensionUnobstructed pulmonary venous returnTo minimize secondary pulmonary artery hypertensionMinimize likelihood of pulmonary artery distortionAvoid dysrhythmiasAll these goals, achieved in a timely fashion, circumvent the major risk factors as long as poor outcome post-Fontan:Ventricular hypertrophy causing diastolic dysfunctionElevated PVR or pulmonary artery pressureAV valve regurgitationVentricular systolic dysfunctionThe reasons why the above hurt the post-fontan heart will be discussed later

Stage I – Norwood palliationThe goal of the Norwood is to stabilize in addition to balance the parallel circuit, protect the pulmonary vascular bed in addition to preserve ventricular functionAdequate oxygen delivery allows as long as the growth necessary as long as a hemi-fontan or BDG to be per as long as medNative ascending in addition to transverse aortic arch is incorporated into a neo-aortaNeo-aorta created by augmenting native arch with autologous pulmonary homograftNeo-aorta is attached to the proximal pulmonary artery trunkNeo-aorta provides systemic outflowImportant that the neo-aorta is free of obstructionObstruction is poorly tolerated by the single ventricle in addition to is associated with increased interstage mortality

Distal MPA is closed Pulmonary flow is provided by a restrictive shunt from the right innominate artery to the RPAModified BTSPost-Norwood AnatomyPost-Norwood issuesThe hope is that nowRBTS + Rp = RsSo the circulations are balanced in addition to volume work is minimizedMeaning as long as a given required Qs, total Q can be less as the ratio is more favorableBut

The ventricle has just been through hypothermic cardiopulmonary bypass with myocardial ischemia/arrestVascular endothelium of the systemic in addition to pulmonary circulations have also been subjected to bypass in addition to injuryCombined effect is a systemic inflammatory in addition to adrenergic stress responseThe ventricle can also exhibit a low cardiac output syndrome in the first 12-24 hours post opAll vascular beds show signs of endothelial dysfunctionEvidenced by increased resistanceThis may tip the balance of flow towards the pulmonary circulationSystemic oxygen dem in addition to s may be unable to be met by the post-op ventricleLeading to anaerobic metabolism, acidosis in addition to worsening functionLCOSLow Cardiac OutputLow systemic cardiac output can be due toGlobally decreased ventricular functionElevated Qp:QsAV valve regurgitationHow to discern between the above

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EchocardiographyEvaluates pump function in addition to rules out AV valve regurgArterial-venous oxygen saturation differenceAn A-V DO2 more than 40% suggests inadequate tissue delivery of oxygen in addition to low systemic cardiac outputOR Lactate level plus base deficitGood echo function plus high A-V DO2 = Qp>QsTreatmentOne must pay attention to both TOTAL CO in addition to the Qp:Qs ratioThe ratio can be altered by maneuvers discussed in my last talkTotal CO can be increased by careful selection of vasoactive agentsWant to avoid tachycardia in addition to increasing afterloadMilrinoneNesiritideDopamineHypoxemiaPulmonary Venous desaturationAtelectasispulmonary edemapneumothoraxSystemic venous desaturationAnemiaLow cardiac outputDecreased pulmonary blood flowElevated PVRPulmonary venous hypertensionPulmonary artery distortionRestrictive systemic to pulmonary shuntGotta rule out the top two, then, think about echo or cath to rule out the anatomic causesWhich need a surgeon .

Coronary circulationSingle right ventricle coronary blood flow occurs predominantly in diastoleLike an in series LVWhen pulmonary flow is supplied by a shunt from a systemic artery, increases in SVR lead to increased pulmonary flow, in addition to increased diastolic pulmonary run-offThis can lead to myocardial ischemia . in addition to sudden deathWhich is why“Leaving a kid in Norwood physiology is like taking a walk through Watts at midnight” Dr. Cocalis The Wall of WoSudden death post NorwoodUnpredictable in addition to suddenExperienced centers report survival between 63-94%1Inter-stage mortality of 10-15%2Rapid fall in PVR, or increase in SVRSteal from coronary arterieslower pressure in pulmonary circulation throughout cardiac cycleThe Journal of Thoracic in addition to Cardiovascular Surgery 2003;126(2) 504-509Arch Dis Child Fetal Neonatal Ed 2005;90:F97-102.

CyanosisAGAIN Pulmonary Venous desaturationAtelectasispulmonary edemapneumothoraxSystemic venous desaturationAnemiaLow cardiac outputDecreased pulmonary blood flowElevated PVR in those with fenestrationPulmonary venous hypertensionArrhythmiasAtrial in addition to ventricular pacing wires are in placeLoss of AV valve synchrony is badDecreases CO, increases required transpulmonary pressure gradientGiven the extent of this lecture, in addition to how vast a subject arrythmias are You got the wires . in addition to the box figure something out.Usual bothersome arrhythmias are atrial in nature, so pacing the atria at a rate higher than the intrinsic rate will fix the issueSame goes as long as a fast junctional rate .ReferencesChang et al, Pediatric Cardiac Intensive Care, LWW, 1998Schwartz S et al, Single Ventricle Physiology, Critical Care Clinics 2003;19:393-411Walker SG, et al, Single Ventricle Physiology – Perioperative implications, Seminars in Ped Surg, 2004, 188-202

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